1. Field of the Invention
The present exemplary embodiment relates to bed support media. It finds particular application in conjunction with support media for a catalyst bed, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
2. Discussion of the Art
In some catalytic reactors, a catalyst bed is formed of a carrier material, typically comprising particulate elements, which supports a catalytic material, such as a metal or metal oxide. Carriers, or catalyst supports, as they are often known, are commonly inorganic materials such as refractory inorganic materials, for example alumina-, silica-, or titania-based compounds, or combinations of these, such as alumina-silica carriers. Carriers may also be formed from carbon-based materials such as, for example, charcoal, activated carbon, or fullerenes. The carrier may have a porous or open structure, such as a ring, honeycomb, or wagon wheel, which provides a large geometric surface area on which the catalyst is supported.
Where the catalyst bed is relatively shallow, the bed may be supported on a foraminous plate, crossed beams, or a similar structure. For beds of greater depth, and consequently greater weight, the catalyst bed is supported in a tower, on a second bed, or support bed, which is typically formed of individual ceramic spheres. Spheres are used to have sufficient strength to support the weight of the catalyst bed and, in the case of the lowermost spheres, the entire weight of the support bed. The spheres are generally of larger diameter than the elements of the catalyst bed that they support. The spherical elements in a support bed have a void fraction, measured as a percentage, of up to about 36%, due to the spaces between the elements. These spaces or voids allow the reactant material to pass through the support bed either before or after coming into contact with the catalyst bed above, depending on the direction of flow. Pellets have also been used as support elements, which, due to their shape, may have slightly higher void fraction than spheres.